A turnstile of this kind, which locks in the stop position, such as is described, for example, in WO-A-90/8875 is provided with a torsionally elastic coupling that permits a slight amount of rotation despite the fact that the blocking arms are locked, and is monitored by an angle of rotation identification system. In one embodiment, the locked stop position is held by an electric motor which, once the control system permits passage, is rotated further into the next stop position after the user pushes against the turnstile. In the event of illicit rotation the motor is not started but reinforced by a mechanical brake.
A turnstile that is similarly powered by a motor is described in DE-C-38 31 056; in this, the motor is started after an impulse that is provided by the user. A brake is triggered electrically so as to act counter to any illicit rotation.
A further turnstile with access control, in which the stop position is fixed by means of an electronically controlled brake, is described in GB A2 186 618. In the event that unimpeded passage is to be provided, slow and continuous operation by means of a motor can be effected.
In the case of monitored passageways that provide for controlled passage by turnstiles, on the one hand the behaviour or the customary actions of the users, and, on the other hand, specific safety criteria, have to be considered. A turnstile that is released as a result of positive monitoring may not be rotated immediately by a motor; rather, it must be rotated by the user as soon as he is ready to pass through it. In this case, the rotation of the turnstile that has been released is effected by the pressure of the user's body against the blocking arm, when the locking resistance must be overcome. Only the overcoming of this locking resistance indicates, on the one hand, readiness to pass through, and, on the other hand, the correct position of the user, so that the subsequent motorized movements takes place at the anticipated time. Overcoming the locking resistance can be problematic, not only for children, but also, in particular for adults at the access points to T-bar ski lifts, when it must not be forgotten that the following blocking arm swings into position behind the user.